To install a new windshield wiper blade, lift up the old blade, press the tab on the underside, and slide the old blade off the wiper arm. Finally, line up the new windshield wiper blade with the hook, and pull it tight until you hear a click.
The windshield wiper arm pulls out easily so that it is perpendicular to the windshield. Once pulled out, the arm stays in the extended position on its own. This is the position you need when replacing the blade.
A small tab on the underside of the arm holds the wiper in place. By pressing this button, you release the old blade so you can remove it easily. Use caution once you remove the old blade. The empty arm can scratch or damage the windshield if it snaps up against it. Placing a towel on the windshield is one way to protect the glass.
The new wiper blade clip needs to line up with the hook-like end on the wiper arm. If you don't line up the new wiper blade correctly, you can't secure it in place. An upward motion clamps the hook over the rounded clip portion of the blade. Listen for the click to know it is securely in place. Press the arm back toward the windshield so the new wiper blade rests against the glass.